I propose to determine the number, and study the structure and differentiation of immunoglobulin genes by molecular hybridization and cloning procedures. The immune system is an extremely interesting system since it is likely that unusual genetic mechanisms are involved in the differentiation of antibody genes. Specifically, I plan to continue my studies using nucleic acid hybridization to determine the number of genes for the variable regions of immunoglobulin kappa chain in the mouse in an attempt to decide between the germ line and somatic mutation theories for the generation of antibody diversity. I also plan to isolate genes for immunoglobulin kappa chain by recombinant DNA technology in order to study their structure and arrangement. This should lead to an understanding of how the variable and constant region genes join, and whether and how somatic mutation of the variable genes occurs.